Method and apparatus for evaporating sulphate residual liquor



B. s. NYQUIST Filegi Harsh 17. 19:59

April 29, 1941.

METHOD AND APPARATUS FOR EVAPORATING SULPHATE RESIDUAL LIQUOR I; A TTORIVEYS Patented 29, 1941 METHOD AND APPARAT IN G SULPHATE RE US FOR EVAPORAT- SDJUAL LIQUOR Btirje Sune Nyquist, Sandviken,

Dynas, Sweden,

assignor to Aktiebolaget Svenska Flaktfabriken, Stockholm, Sweden, a joint-stock company of Sweden Application March 17, 1939, Serial No. 262,486

In Sweden January 5, 1937 z ciaims. (Cl. 159-10) This invention relates to the treatment of residual liquor which is produced in the sulphate process of manufacturing pulp from cellulosic fibrous materials.

In the manufacture of pulp according to the sulphate process the sulphate residual liquor (black liquor) is concentrated to a viscous condition by means of disc evaporators (Scheibenverdampfer) in the recovery process. 'I'his.viscous liquor is then evaporated to dryness in rotating furnaces and finally burnt insoda melting furnaces, the melted soda being then caustifled with lime, whereby so called white liquor is obtained, which is used in the cooking process.

The present invention relates to a method according to which the sulphate residual liquor by means of, for instance, flue gases may be directly evaporated to dryness.

According to the invention a film of the liquor is caused to follow a rotating body, the surface of which is, at least partially, swept by hot gases (moving either in the direction of travel of, or counter to the direction of, the body) in such a manner that the liquor adhering to the body is evaporated to dryness by the action of the hot gases, the dried material being then scraped off by scraping means. v

The apparatus according to the invention may comprisea container for the liquor having an inlet and outlet for the hot cases, a rotary body being provided therein, in the path of the hot gases from the inlet to the outlet, in such a manner that it partially dips into the liquor, and

scraping means provided close to the surface of the body, the said scraping means removing the dried material from the body.

The rotary body may comprise a plurality of spaced discs mounted on a rotatable shaft; or,

it may comprise a substantially cylindrical body carrying on its periphery a plurality of spaced annular projections of disc form integral with said body, the cylindrical body being supported for rotation about the axis thereof. In either event, the scraping means is positioned within.

the' grooves made by, and contacts the surfaces of, the discs or disc-like annular projections in a. manner adapted to remove from said surfaces material carried thereon.

-. residual liquor to dryness by In the accompanying drawing one embodiment of an apparatus according to the'invention is illustrated. Fig. 1 shows a section through the device perpendicularly to the shaft of the rotary body. Fig. 2 is a section of one end portion of the device, taken perpendicularly to the section of Fig. 1, and Fig. 3 shows a detail.

4 of about cylindrical shape, the surface of which substantially corresponds to the periphery of the circular discs 2. The container 4 is filled .with sulphate residual liquor 5 to such a level that the discs 2 partially dips into the same. A pipe 8 through which hot exhaust gases are supplied,-

for instance from the soda melting furnace, is provided with an opening that extends all alo the container 4. In each space between the circular discs 2 there is provided an inclined scraper 1 which extends as far as to the spacer 3.

The shaft l rotates in the direction of the arrow and the liquor will adhere to the discs 2. These discswill during the rotation meet a current of hot gases from the pipe 6. The speed of rotation ,of the shaft l is adjusted in such a manner that the liquor adhering to the discs has been evaporated to dryness when it reaches the scrapers I. These scrapers l scrape off the dry material, which falls down into a channel 8 located beneath the scrapers, and having a transport screw 9 provided therein. Thecooled gases escape through the. pipe It to, for instance, the stack. In order to allow the entering gases to contact the liquor and the portions of the discs 1 located beneath the scrapers (the scrapers prevent the gases to escape this way) there is provided a slot ll between the container 4 and the holder l2 for the scrapers. This slot, which extends all along the container 4, communicates with a channel l3, connected with the pipe 6 through conduit H as indicated by dotted lines in Fig. 1. The size of the slot is so adjusted that a smaller part of the hot gases flows in be neath the scrapers.

The discs 2 are preferably constructed in such a manner that they grow thinner towards the periphery (see Fig.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In an apparatus for evaporating sulphate means of hot gases, the combination with a chamber whose lower part provides a container for liquor, a gas inlet extending along one side of said chamber, a gas outlet at an opposite side of said chamber, means for passing a stream of hot gases through said chamber from inlet to outlet, a rotary body positioned between said inlet and said outlet'and in and substantially transverse to the path of such stream, said rotary body comprising a 'plurality of annular projections of disc form andbeing so located that said annular projections partially extend into said liquor-containing part of said chamber, and scraper means cooperating with surfaces of said annular projections to remove material therefrom and so positioned as to constitute a bailie directing the flow of gas from inlet to outlet over the axis of said rotary body,

of a supplemental elongated opening .in said chamber along the side thereof containing'said inlet, said supplemental opening being below said scraper means and adjacent the liquor-containing part of said chamber, and means for introducing into the chamber, through said supplemental opening, a supplemental stream of hot gas for traversing the lower portions of said annular projections.

; ing support, the improvement which consists in dividing the current of hot flue gas into two separate currents prior to passage thereof 'into contact with the liquor, passing one of said currents over the surface of the body of liquor, and

separatelypassing the other of said currents over said film of liquor.

BoRJE SUNE NYQUIST. 

